in beam/src/main/scala/magnolify/beam/RowType.scala [266:276]
implicit def rfOption[T](implicit f: RowField[T]): RowField[Option[T]] = {
new Aux[Option[T], f.FromT, f.ToT] {
override def from(v: f.FromT)(cm: CaseMapper): Option[T] =
if (v == null) None else Some(f.from(v)(cm))
override def to(v: Option[T])(cm: CaseMapper): f.ToT = v match {
case None => null.asInstanceOf[f.ToT]
case Some(x) => f.to(x)(cm)
}
override def fieldType(cm: CaseMapper): FieldType = f.fieldType(cm).withNullable(true)
}
}